As disclosed in Chinese Patent No. CN 2218768Y, the present expanding apparatus, such as a hydraulic aviate former for piles with multi-branch bearing plates, is a multi-branch bearing plate pile machine designed to increase its bearing capacity and tensile strength. With this machine, construction of a pile is completed by drilling a hole, expanding the hole, and pouring concrete into the holes. The multi-branch bearing plate hole expanding apparatus is a special equipment for forming the side cavities of the pile holes to be fulfilled with concrete, which is suitable not only for poured piles, but also for anchor struts. It is proven that the pile so built has the features of increased load bearing capacity and reduced amount of concrete poured into. However, the extended tube of this expanding apparatus is rigidly coupled by connecting steel pipes one segment after another and is lifted and dropped unto a determined depth of a hole by a crane to perform an expanding operation. After one expanding operation is completed, the bow pressing arm is retracted and revolved to the next position with the aid of a thinner steel tube extending through a hole on the steel arm and expanding operation starts again.
To complete expanding of an entire cavity, the steel arms have to be revolved 8-9 times. The reason to have a rigid coupling of steel pipes is to achieve these functions:
(a) torque transmission, PA1 (b) tension transfer, and PA1 (c) measurement of the depth of the working device in a hole.
If the expanding operation takes place at the bottom of a hole of 40 m-50 m deep, an extended steel tube has a diameter of 280 mm, a wall thickness of 14 mm, and a length of 40 m-50 m and the working device has to be lowered down into the hole. The extended steel tube weighs to tens of tons, which makes vertical movement of the long extended tube difficult, resulting in labor and time wasting. Furthermore, when an extended tube is in a hole at tens of meters deep, there is likely offset vertically, which may cause the steel tube stuck in the hole. Especially when expanding, a pressure force of hundreds of tons is applied to both sides of the hole, so the steel tube inclines towards one direction if the angle of the pressure force is applied offset, resulting in a side force increased by tens of times. As a result, the connecting bolt and shaft pin may be broken so that the expanding device may fall down into the hole. In addition, the prior art apparatus may not accurately measure the depth the tube drops down and thus, the layer underground can not be located accurately. This inaccurate location leads to error on the load bearing capacity and creates poor piles.
Besides, there is an outer tube outside the bow pressing arm, which not only increases the weight of the apparatus, but also brings soil with it while the bow pressing arm is retracted. It is even worse when the expanding operation is performed at a layer of sand and stones since stones brought into the tube may stick the bow pressing arm from being retracted. In this case, it is impossible to lift up the apparatus from the hole as the bow pressing arm cannot be retracted to its normal position. In addition, prior art expanding apparatus neither detects the status of the soil being expanded, nor tests the expanding operation. Therefore, concrete pouring processing in construction of a pile has to be stopped once collapse happens, thus, what is needed is an extending apparatus that may be smoothly moved in a hole to complete expanding process.